This proposal is designed for the organization and development of natality data bases which will permit exploration of a series of questions pertaining to obstetrical practice and perinatal outcomes. The bringing together of a group, with diverse backgrounds of public health, biostatistics, epidemiology, demography and pediatrics, will permit the posing of questions, the development of analytic plans, statistical data processing and the interpretation of results from a variety of viewpoints. Rapidly evolving concepts of obstetrical management have resulted in widely disparate approaches, measurably in patt through the available data sets. Jeffcoat (1976) has warned that "obstetricians have to be wary of becoming over-confident in their ability to do better than Nature and thus intervene too much - like others, they have to examine critically and objectively their present practices with a view to excluding procedures which are superfluous, wasteful, of doubtful usefulness and sometimes harmful." The present proposal is intended as an initial step in that critical and objective examination using population based natality data collected over the past decade in urban, suburban and rural settings.